DTC Advanced Diagnostics: P15C9
DTC P15C9: Brake Booster Pressure Sensor A Output Voltage Locked
General Description
The powertrain control module (PCM) calculates a vacuum pressure (differential pressure between barometric pressure) in the brake booster based on the brake booster pressure sensor output voltage, and it is used to judge auto idle stop permission. The PCM stores the DTC because of the brake booster pressure sensor malfunction when the value for the brake booster pressure sensor does not fluctuate while repeating the sequence of "vehicle stop"->"vehicle start"->"vehicle stop" for a predetermined number of times (it is a situation that the brake booster pressure value should drop due to the braking operations or should increase/decrease due to the negative pressure being applied from the supply source).
Monitor Execution, Sequence, Duration, DTC Type, OBD Status
| Execution | Continuous |
| Sequence | None |
| Duration | - |
| DTC Type | One drive cycle, MIL off* |
*: Auto idle stop indicator (amber) blinks.
Enable Conditions
| Condition | |
|---|---|
| No active DTCs set (prevents monitor from running) | P0555, P0557, P15C5, P15C7 |
| Other | After engine warmed up |
| Vehicle stopped at 0 mph (0 km/h) for at least 3.5 seconds | |
| Take 4.5 seconds to 9.2 seconds to stop from vehicle speed [VEHICLE SPEED] at 19 mph (30 km/h) | |
| No wheel spin is detected | |
| Dual speed sensor, barometric pressure (BARO) sensor, and engine coolant temperature (ECT) sensor must not be malfunctioned |
[ ]: HDS Parameter
Malfunction Threshold
The fluctuation of the brake booster pressure sensor value is less than 1 kPa (0.4 inHg, 9 mmHg) while repeating the sequence of "the vehicle speed is 19 mph (30 km/h) -> 0 mph (0 km/h) -> 19 mph (30 km/h)" for five times (it is a situation that the brake booster pressure value should drop due to the braking operations or should increase/decrease due to the negative pressure being applied from the supply source).
Possible Cause
- Booster check valve stuck closed
- Vacuum hose clogged
- Brake booster pressure sensor failure
- PCM internal circuit failure
Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected, the auto idle stop system indicator (amber) comes on and a Pending DTC, a Confirmed DTC, and the freeze data are stored in the PCM memory. The MIL does not come on.
Conditions for clearing the DTC
The auto idle stop system indicator (amber) is cleared if the malfunction does not return in next trip in which the diagnostic runs. The auto idle stop system indicator (amber), the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the 12 volt battery.